Effect of Field Pea Level on Intake,
Digestion, Microbial Protein Synthesis, Ruminal Fermintation, and Fill in Beef Steers
Fed Growing Diets
J.J. Reed, G.P. Lardy, M.L. Bauer, J.S. Caton, T.C. Gilbery
he effects of increasing level of field pea (var: Profi) level on intake, digestion, microbial protein synthesis, ruminal fermentation, and fill were evaluated in beef steers fed growing diets. Four ruminally and duodenally cannulated crossbred beef steers (367 ± 48 kg initial BW) were used in 4 x 4 Latin square design. The control diet consisted of 50% corn, 23% corn silage, 23% alfalfa hay, and 4% supplement (DM basis). Field pea replaced corn at 0, 33, 67, and 100%, forming the treatments. Diets were formulated to contain a minimum of 12% CP, 0.62% Ca, 0.3% P, and 0.8% K (DM basis). Each period was 14 d in length. Steers were adapted to the diets for 9 d. On d 10 to 14, intakes were measured. Field pea was incubated in situ, beginning on d 10, for 0, 2, 4, 8, 12, 16, 24, 36, 48, 72, and 96 h. Bags were inserted in reverse order and all bags were removed at 0 h. Ruminal fluid was collected and pH recorded at –2, 0, 2, 4, 6, 8, 10, and 12 h post-feeding on d 13. Duodenal samples were taken for three consecutive days beginning on d 10 in a manner that allowed for a collection to take place every other hour on a 24 h clock. Linear, quadratic, and cubic contrasts were used to compare treatments. There were no differences in DMI (12.46 kg/d, 3.16% BW; P > 0.46). Ruminal dry matter fill (P = 0.02) and mean ruminal pH (P = 0.01) decreased linearly with increasing level of field pea. Ruminal ammonia-N (P < 0.001) and total VFA concentrations (P = 0.01) increased linearly with increasing level of field pea. Total tract disappearance of OM (P = 0.001), N (P < 0.001), and NDF (P = 0.004) increased linearly with increasing level of field pea. There were no differences observed in total tract disappearance of starch (P = 0.5) or ADF (P = 0.27). Stomach disappearance of N corrected for microbial matter (P = 0.02) and stomach disappearance of NDF (P = 0.004) increased linearly with increasing level of field pea. There were no differences in stomach disappearance of OM (84.8%; P = 0.9), starch (91.7%; P = 0.77), or ADF (77.6%; P = 0.77). Treatment did not effect microbial efficiency (7.6 g N/kg of true OM digestion, P = 0.27). There were no differences in in situ 0 h disappearance (P = 0.40), slope (P = 0.16), or intercept (P = 0.19). Rumen degradability responded cubically (P = 0.04) as it increased from 0 to 33, decreased from 33 to 66, and increased from 66 to 100% field pea inclusion. Because of their relatively high level of protein, including field peas in growing diets will reduce the need for protein supplementation and may reduce feed costs. It appears field pea is a suitable substitute for corn in growing diets.
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